Wireless communications systems are widely deployed to provide various types of communication such as voice, packet data, and so on. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or other multiple access techniques. Such systems can conform to standards such as Third-Generation Partnership Project 2 (3gpp2, or “cdma2000”), Third-Generation Partnership (3gpp, or “W-CDMA”), or Long Term Evolution (“LTE”). In the design of such communications systems, it is desirable to maximize the capacity, or the number of users the system can reliably support, given the available resources.
In an aspect of a wireless communications system, transmissions between two units often employ a degree of redundancy to guard against errors in the received signals. For example, on a reverse link (RL) transmission from an access terminal (AT) to a base station (BS) in a cdma2000 wireless communications system, redundancies such as fractional-rate symbol encoding and symbol repetition may be employed. In a cdma2000 system, encoded symbols are grouped into sub-segments known as power control groups (PCG's) and transmitted over the air, with a fixed number of PCG's defining a frame.
While signal redundancy such as that employed in cdma2000 may allow accurate recovery of transmitted signals in the presence of noise, such redundancy may cause unnecessary interference to other users of the wireless communications system, e.g., to other AT's communicating with the BS on other reverse links. This interference may undesirably decrease the system capacity.
It would be desirable to provide techniques to improve the efficiency of digital communications systems employing redundancy.
In a further aspect of a wireless communications system, transmissions between two units may include a traffic signal and a pilot signal having known data content. While the pilot signal may aid the receiver, e.g., a BS, in recovering data from the traffic signal, the pilot signal sent by one AT may undesirably cause interference to the traffic and pilot signals sent by other AT's to the BS. It would be desirable to provide techniques to improve the accuracy of demodulating and decoding traffic signals in the presence of pilot interference.